What Causes a Car to Start Easily When Cold but Not When Hot?
3 Answers
Main reasons include the following aspects: 1. Fuel injector leakage: While fuel injection is normal operation, leakage constitutes additional fuel supply. The more severe the injector leakage, the richer the air-fuel mixture becomes, leading to difficulty starting when hot. 2. Faulty carbon canister purge valve: During hot starts, fuel atomization is already normal and doesn't require additional fuel vapor. If the carbon canister continues supplying vapor to the intake, it creates an over-rich mixture, making starting difficult. 3. Intake air temperature sensor malfunction: This sensor adjusts fuel injection quantity. If faulty, it causes hard starting when the engine is hot.
The other day when I drove to work, I noticed there was no problem at all when the car was first started, but after it warmed up and I tried to restart it, it wouldn't fire up, which was really frustrating. I think the issue could be in a few areas: the fuel pump is prone to problems when it's hot, such as internal temperature causing fuel vaporization and vapor lock, preventing fuel from flowing; or the ignition system fails when hot, with spark plugs or ignition coils not conducting properly when overheated, failing to ignite. Additionally, sensors like the crankshaft position sensor might malfunction under high temperatures, affecting the computer-controlled fuel injection. It's important to regularly check the vehicle, especially during maintenance, to clean carbon deposits and ensure the fuel lines are clear. If you encounter this hot-start issue, it's advisable to first measure the fuel pressure or check if the relay is functioning properly. For long-term prevention, consider installing some heat insulation or upgrading to more heat-resistant components, which can significantly reduce trouble.
I noticed this phenomenon is quite common when researching cars. Cold starts go smoothly, but the car won't start when hot. The main reasons could be issues with the fuel system, where hot fuel evaporates and forms vapor locks or blockages in the lines. It might also be due to faulty sensors in the electronic control system, such as temperature sensors failing under high heat, causing the air-fuel mixture to be too rich or too lean. Other factors include excessive hot air from intake manifold leaks or poor heat dissipation in ignition components. It's recommended that owners avoid shutting off the engine immediately after starting; instead, let it cool down gradually. Regularly clean the throttle body and check wiring connections to prevent aging. In the long run, choosing components designed for high-temperature resistance will be more reliable.
